Your Digest for Sunday, Jan 07, 2024 10:59 AM

Broadly, lymphoma is distinguished from leukaemia in its clinical presentation, where lymphoma predominately involves lymph nodes, and leukaemia the blood and bone marrow, and by the fact that lymphomas arise from cells that reside in the lymphatic system rather than in the bone marrow. However, in the context of the cell of origin this is perhaps a rather nebulous distinction, and there is evidence that chronic lymphocytic leukaemia (CLL) may emerge in differentiated/mature lymphocytes in the periphery
[!INFO] The correct identification of AML vs ALL is veryimportant as a determines treatment.

• Aggressive cancers
• Child with lymphocytosis must be evaluated. Hepatosplenomegaly, complaining of bone pain / limp are red flag signs!
• investigations focus on identifying haematologic malignancy and then identifying the type of malignancy (myeloid or lymphoid, subtypes of lymhpoid etc)

• Blasts can be of B cell lineage (commonest - 85%), T cell (15%) and NK cell (<1%). These can be distinguished by cell surface antigens.
  • T cell leukemias are commoner in 15-20 year olds and in males.
  • (Mnemonic: T for twenty)

Note : T cells are the commonest type of lymphocytes in healthy states, followed by B and NK cells.

• Can present as leukemi (blasts in blood with bone marrow involvement) or lymphoblastic lymphoma (mediastinal mass)

• Symptoms are non specific, similar to self limited diseases
• Fever (common), pallor, bleeding (+/-petechial rash), bone pain (can present as limp!, #hepatosplenomegaly, lymphadenopathy - HSM is the commonest clinical finding
• CNV involvement: headache, vomiting, nerve palsies from meningeal spread.
• WBC can be low, normal or high.
  • When gross malignant lymphocytosis develops, anaemia, thrombocytopaenia and neutropenia have usually developed.
• Peripheral blood can sometimes have no blasts but bone marrow will show blasts.

• B-type ALL (i.e of B lymphocytes) have the philadelphia chromosome. (9;22 translocation)

• more than 20% lymphoblasts
  

2. Philadelphia chromosome positive

• Above is an image of the atypical lymphocytes in infectious mononucleosis. They represent activated T lymphocytes.
• Basophilic skirting occurs where lymphocyte cytoplasms abuts erythrocytes. Source

• #lymphadenopathy: Symmetrical, tender, posterior chain predominant
• Blood - lymphocytosis with atypical lymphocytes (mononuclear cells) - hence the name infectious mononucleosis.

• Chronic active EBV infection - Persistent IM like syndrome with continued viraemia. It's a life threatening lymphoproliferative disorder.
  EBV should be differentiated from Acute lymphoblastic leukemia which can occur in the same age group and have similar initial presentation.